1. Field of the Invention
The present invention relates to packaging materials and, in particular, to a plastic bag for vacuum packaging of perishable items.
2. Discussion of the Prior Art
There is a need for a bag adapted for use in either a home or a commercial environment such that it may be easily evacuated and then heat sealed for the vacuum packaging of perishable items.
U.S. Pat. No. 3,809,217 titled "Packaging for Flat Objects", issued to Harrison on May 7, 1974, describes a two-layer packaging material that consists of a flat outer layer of paper or plastic film joined with an embossed inner layer of heat sealable polystyrene. However, owing to the configuration of the embossed pattern of the polystyrene inner layer, air pockets are trapped between the inner and outer layers, rendering the material unsuitable for vacuum packaging of perishable items.
Most heat sealable thermoplastics, including polystyrene and food-safe polyethylene and polypropylene, are gas permeable materials. Thus, air trapped between the two layers of the Harrison packaging material will diffuse into the interior of the bag, spoiling the perishable items contained therein. Furthermore, the Harrison packaging material is intended as a relatively stiff container for protecting flat objects from physical damage and for making it difficult to identify their surface structure by feeling the package. Few perishable items are inherently flat, rendering the Harrison packaging material unsuitable for applicant's primary intended purpose.
U.S. Pat. No. 4,093,068 titled "Packing Sheet and Packages Formed Thereby", issued to Thomas J. Smrt on June 6, 1978, also describes a two-layer material for packaging objects. The Smrt material features air pillows which protrude into the interior of the resulting package in order to hold the contents more firmly. Thus, for the same reasons stated above with respect to the Harrison packaging material, the Smrt material is also not suitable for vacuum packaging.